The present invention relates, in general, to intraluminal medical devices, and, more particularly, two a new and useful stent, stent delivery apparatus and method for stenting a vessel using a stent with interlocking elements.
A stent is commonly used as a tubular structure left inside the lumen of a duct to relieve an obstruction. Commonly, stents are inserted into the lumen in a non-expanded form and are then expanded autonomously (or with the aid of a second device) in situ. When used in coronary artery procedures for relieving stenosis, stents are placed percutaneously through the femoral artery. In this type of procedure, stents are delivered on a catheter and are either self-expanding or, in the majority of cases, expanded by a balloon. Self-explanding stents do not need a balloon to be deployed. Rather the stents are constructed using metals with spring-like or superelastic properties (i.e., Nitinol), which inherently exhibit constant radial support. Self-expanding stents are also often used in vessels close to the skin (i.e., carotid arteries) or vessels that can experience a lot of movement (i.e., popliteal artery). Due to a natural elastic recoil, self-expanding stents withstand pressure or shifting and maintain their shape.
As mentioned above, the typical method of expansion for balloon expanded stents occurs through the use of a catheter mounted angioplasty balloon, which is inflated within the stenosed vessel or body passageway, in order to shear and disrupt the obstructions associated with the wall components of the vessel and to obtain an enlarged lumen.
Balloon-expandable stents involve crimping the device onto an angioplasty balloon. The stent takes shape as the balloon is inflated and remains in place when the balloon and delivery system are deflated and removed.
In addition, balloon-expandable stents are available either pre-mounted or unmounted. A pre-mounted system has the stent already crimped on a balloon, while an unmounted system gives the physician the option as to what combination of devices (catheters and stents) to use. Accordingly, for these types of procedures, the stent is first introduced into the blood vessel on a balloon catheter. Then, the balloon is inflated causing the stent to expand and press against the vessel wall. After expanding the stent, the balloon is deflated and withdrawn from the vessel together with the catheter. Once the balloon is withdrawn, the stent stays in place permanently, holding the vessel open and improving the flow of blood.
In the absence of a stent, restenosis may occur as a result of elastic recoil of the stenotic lesion. Although a number of stent designs have been reported, these designs have suffered from a number of limitations. Some of these limitations include premature deployment of the stent due to circumstances such as over-manipulation when traversing tortuous vessels or the inability to maintain the stent secured to the balloon due to migration, slippage, etc.
Accordingly, to date, there have not been any stent designs, that specifically address these drawbacks in an efficient and cost effective manner.
The present invention relates to an apparatus and method for stenting a vessel in conjunction with a particular new and useful stent having a lattice of interconnecting elements defining a substantially cylindrical configuration. The lattice has a first open end and a second open end wherein the lattice is movable between a locked configuration and an open configuration.
One embodiment of the stent includes a plurality of bridges connecting the interconnecting elements wherein each bridge interlocks with an adjacent bridge in the locked configuration and wherein each bridge separates from the adjacent bridge in the open configuration.
In another embodiment, the interlocking elements include a plurality of struts wherein each strut interlocks with an adjacent strut in the locked configuration and each strut separates from the adjacent strut in the open configuration.
For the interlocking bridge embodiment, each bridge has a projection and a base wherein the base has a projection holding section for receiving the projection from an adjacent bridge. Likewise, for the interlocking strut embodiment, each strut has a projection and a base wherein the base has a projection holding section for receiving the projection from an adjacent strut. Accordingly, for both of the stent embodiments identified above, several features are in common. For instance, the interlocking elements comprise a plurality of adjacent sections. Additionally, the adjacent sections comprise adjacent hoops wherein each hoop comprises a plurality of loops. Each loop comprises at least one strut.
For both the interlocking bridge embodiment and the interlocking strut embodiment, lateral arms extend from the base. Moreover, the projection holding section of the base has an opening therein for receiving the projection. An extension is connected between the base and the projection, and, for the interlocking bridge embodiment, the extension includes a neck wherein the projection is located at a superior position on the neck.
The projection also includes at least one lateral lip and the projection holding section includes at least one lateral ledge for releasably engaging the at least one lateral lip of the projection. The projection also includes at least one sidewall adjacent to the at least one lateral lip. Additionally, the projection holding section includes at least one lateral depression adjacent to the at least one lateral ledge for releasably engaging the at least one sidewall of the projection.
Although these features are intended to encompass any suitable configuration, in a preferred embodiment, the at least one sidewall is curved and the at least one depression is curved wherein these elements are aligned, snapped-fit or interlock in a puzzle-lock manner. Moreover, the lateral arms of the base connect directly to the interconnecting elements of the lattice.
The stent of the present invention is directed toward both a balloon actuated stent and a self-expanding stent. The stent is made of any suitable material. In one embodiment, the stent is made of an alloy such as stainless steel. In another preferred embodiment, the stent is made of a nickel titanium (Nitinol) alloy. Moreover, this material or any other super-elastic alloy is suitable for the stent according to the present invention. In these self-expanding stent embodiments, the stent is a crush recoverable stent.
The present invention is also directed toward an apparatus and method for stenting a vessel utilizing the stent embodiments described above, e.g., a stent having a lattice of interconnecting elements and including interlocking features such as a plurality of interlocking bridges in one embodiment or a plurality of interlocking struts in another embodiment.
The apparatus further includes a catheter having an inner sleeve and an expandable member on the inner sleeve wherein the expandable member is movable between a collapsed state and an expanded state. One of the stent embodiments described above is secured to the catheter over the expandable member when the expandable member is in the collapsed state and the stent is in the locked configuration. The stent is separated or deployed from the catheter when the expandable member is in the expanded state and the stent is in the open configuration. The apparatus further includes a cover movably disposed over the stent. The cover is an outer sheath made of a polymer material. Additionally, the expandable member is an inflatable balloon.
The method for stenting a vessel according to the present invention comprises the steps of providing the apparatus according to the present invention have one of the stent embodiments, e.g., the interlocking bridge embodiment or the interlocking strut embodiment, and inserting the apparatus within a vessel. The distal end of the apparatus is positioned at a desired location within the vessel and the stent is deployed to the open configuration with the expandable member.
Additionally, the method further includes providing the cover movably disposed over the stent for preventing the stent from moving to the open configuration until desired. The method further comprises deploying the stent to the open configuration by inflation of the expandable member.
Additionally, the method further comprises securing the stent to the catheter by interlocking the bridges (for the interlocking bridge embodiment) or by interlocking the struts (for the interlocking strut embodiment) prior to performing certain steps according to the present invention. Lastly, the method according to the present invention also comprises removing the catheter from the patient after the deployment of the stent.